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ust49wa.theexpertta.com ! Home Studcnt: statenacwu.cdu My Account Log Out Class Management Help HW 8 Begin Date: 1/1/2018 12:00:00 AM Due Date: 3/1/2018 11:59:00 PM End Date: 3/12/2018 11:59:00 PM (20%) Problem 5: If a car takes a banked curve at less than a given speed, friction is needed to keep it from sliding toward the inside of the curve (a real problem on icy mountain roads) Assignment Status Click here for detailed view 50% Part (a) Calculate the minimum speed, in meters per second, required to take a 116 m radius curve banked at 140 so that you don't slide inwards, assuming there is no friction Grade Summary min 0% 100% Problem Status Potential 1 Completed sinO Submissions Attempts remaining: 10 (5% per attempt) detailed view tan() cos) cotan asin acos0 atan acotan sinhO cosh) tanh cotanho Partial 3 Partial END Degrees Radians CLEAR Submit Hint I give up! Hints: 3% deduction per hint. Hints remaining: 3. Feedback: 3% deduction per feedback. 50% Part (b) What is the minimum coefficient of friction needed for a frightened driver to take the same curve at 23 km/h? Allcontent C 2018Expert TA.uc

Explanation / Answer

a) using tan(theta) = v^2/(R*g)

tan(14) = v^2/(116*9.8)

v = 16.83 is the minimum speed

b)
let v^2/(rg) = a

v = 23 km/hr 23*(5/18) = 6.38 m/s

then v^2/(r*g) = 6.38^2/(116*9.8) = 0.0358

then

mu_s = (tan(14)-a)/[1+(tan(14)*a]

mu_s = (tan(14)-0.0358)/(1+(tan(14)*0.0358))

mu_s = 0.21

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